1. Field of the Invention
The invention of the present application relates to a pipe joint for connecting piping.
2. Prior Art
Hetherto, there exists a pipe joint of this type which is provided, as shown in FIG. 10 for example, with a sleeve 5 having an inclined face 50 in a large-diameter hole 11 of a nipple 1, the face inclining in such a way that the diameter of its internal circumferential face diminishes toward an opening in the axial direction, an insert 3 slidably mounted and having a through hole 30 leading to a small-diameter hole 10 of the nipple 1, and a collet 4 having an external circumferential face 40 which can get in contact with the inclined face 50 of the sleeve 5 and designed to be expandable and contractible in diameter when sliding in the axial direction inside the sleeve 5.
However, with the conventional pipe joint mentioned above, it is impossible to fit the three members, or the above-mentioned sleeve 5, insert 3 and collet 4, in the large-diameter hole 11 of the nipple unless it is relatively a deep hole and, therefore, it is necessary to reduce the thickness around the large-diameter hole to a great extent in machining of the nipple 1.
As a result, the machining of the large-diameter hole 11 of this nipple 1 presents such problems as very much of machining even with cutting process and plastic working like forging and difficulty of high-accurate machining thereby.
Moreover, the conventional pipe joint also has a problem of high cost because machining of the sleeve 5 requires cutting with a lathe, etc. to provide an inclined face 50 on the internal circumferential face of the sleeve 5, the face inclining in such a way that the diameter diminishes toward the open side in the axtial direction.
Another problem with the conventional pipe joint is impossibility of reuse of the pipe joint because once a hose H is connected with the pipe joint, they could not be separated from each other.
In addition, the conventional pipe joint also has other problems as described hereunder.
As shown in the drawing FIG. 10, the pipe joint is constructed by installing an insert 3 coaxially and slidably with the nipple in a cylindrical nipple 1 having an external thread on one end, and by placing a collet 4 between the insert 3 and the nipple 1 in a way to allow the collet to advance or retreat freely therein, and is designed to fix a pipe inserted between the insert 3 and the collet 4 in a non-detachable state with the holding force of those memembers.
For that purpose, the nipple 1 is provided with a pipe inserting port 11a at one end as shown in the drawing, and a tapered part 50 diminishing in diameter toward its opening side is formed on the internal circumference near the pipe inserting port 11a.
The collet 4, which is constructed with an elastic material, has an outside diameter slightly larger than the diameter of the pipe inserting port 11a as indicated in the drawing and a slit 42 opening to the pipe inserting port 11a formed on the circumferential wall thereof.
And, the gap between the collet 4 and the insert 3 is set slightly smaller than the thickness of the pipe to be connected to them.
Consequently, inserting a pipe forcibly between the collet 4 and the insert through the pipe inserting port 11a and then pulling the pipe cause the collet 4 and the insert 3 to move toward the pipe inserting port 11a together with the pipe. And, from the time when the collet 4 gets in contact with the tapered part 50, a pressing force from the tapered part 5 acts on the collet 4 in a direction to reduce its diameter and, as a result, the holding power of the pipe by the collet 4 and the insert 3 increases and the pipe is fixed in a non-detachable state.
Namely, this pipe joint is very convenient in that a pipe can be very easily connected by just being inserted in the pipe inserting port 11a and then pulled backward.
However, with the pipe joint of the above-mentioned type, there is a risk that, in case the collet 4 gets worn after a long period of use, the collet 4 may be broken when a connected pipe is pushed therein. In such a case, a stable connecting power cannot be obtained even if the pipe is pulled backward.